In construction, road building and other industries, machines are used to controllably place loose material and convert that material into a supporting substrate. In the context of paving roads, parking lots, etc., a paving machine is typically used to deposit and preliminarily compact a paving material which is later treated via one or more compacting machines to render a relatively hard, smooth traffic-bearing surface.
A conventional paving machine includes a tractor. The tractor includes a material storage hopper and a conveyor to transport material from the hopper and within the tractor to deposit the material onto the work surface being paved. The tractor may also include an auger for spreading the material laterally in front of a grading implement, such as a screed, which is towed behind the tractor and is used to compact and control the thickness and width of the paving material deposited onto the work surface.
For most operations, the storage capacity of the hopper is insufficient to store all the paving material which will be placed by the paving machine. Therefore, it is typically necessary to periodically or continuously resupply the hopper with paving material to be deposited. To this end, supply machines, such as dump trucks, may be used to deposit paving material ahead of the tractor on the work surface to be paved. The tractor may be equipped with a mechanism for loading the hopper with the paving material dumped on the work surface. One known system utilizes a mechanism known as a windrow elevator to elevate paving material from the work surface into the hopper of the tractor. Other strategies include the use of a material transfer vehicle that picks up loads of paving material deposited at a work site and shuttles the paving material to the hopper, on an as-needed basis.
Thus, the hopper receives the paving material and the conveyor deposits the paving material in front of the transversely extending auger. The auger spreads the paving material laterally in front of the grading implement, which compresses and compacts the material downwardly to form a “mat” of paving material, ideally of uniform thickness and surface finish.
A conventional grading implement or screed is of a set width. However, in certain paving applications, such as driveways, parking lots, and the like, varying the asphalt mat width is required. As a result, width-adjustable or extendable screed arrangements have become common for varying the width of the asphalt mat without interrupting the paving process. Typically, extendable screeds consist of a main screed section of a fixed width and hydraulically extendable “screed extenders” that are capable of extending from each end of the main screed section.
In a normal operation of an asphalt paver, an operator can makes adjustments to affect the depth of the asphalt mat being laid. One adjustment that can be made is related to the amount of paving material that is distributed by the auger in front of the screed. If an insufficient amount of material is delivered in front of the screed, the rotational speed of the auger may be increased. If the amount of material delivered in front of the screed is excessive, the rotational speed of the auger may be decreased. Determining whether an insufficient amount of paving material or an excessive amount of paving material has been deposited in front of the screed may include the use of a sonic sensor, as disclosed in U.S. Pat. No. 4,933,853. The sonic sensor directs a sonic signal towards the paving material that has been spread by the auger and the time interval it takes for the signal to bounce back to the sensor is used to determine the height of the material.
However, the position where this measurement will affect the accuracy of the measurement. For example, the measurement is taken may be compromised if the sonic signal engages the paving material too close to or too far away from the auger or the screed. Hence, the position of the sonic sensor is usually adjustable. However, properly adjusting the position or aim of a sonic sensor is problematic as the operator has no visual indication of the exact location of where the sonic signal engages the paving material.
Accordingly, there exists a need for a reliable and easy to use system and method for adjusting the sensors used to measure the amount of paving material deposited in front of grading implements or screeds of paving apparatuses.